Automatic deposition profile targeting

ABSTRACT

A method of automatic deposition profile targeting for electrochemically depositing copper with a position-dependent controllable plating tool including the steps of depositing copper on a patterned product wafer, measuring an actual thickness profile of the deposited copper and generating respective measurement data, feeding the measurement data to an advanced process control (APC) model and calculating individual corrections for plating parameters in the position-dependent controllable plating tool.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure generally relates to the process of depositing amaterial on a substrate using a position-dependent controllabledeposition tool, and, more particularly, to automatic deposition profiletargeting for depositing copper to a predetermined deposition profile.

2. Description of the Related Art

The demand for higher integration, higher clock frequencies and smallerpower consumption in microprocessor technology leads to a new chipinterconnection technology, using copper instead of aluminum for chipwiring. Since copper is a better conductor than aluminum, chips usingthis technology may have smaller metal components and use less energy topass electricity through them. These effects lead to a high performanceof the integrated circuits.

The transition from aluminum to copper, however, required significantdevelopments in fabrication techniques. Since volatile copper compoundsdo not exist, copper cannot be patterned by photoresist masking andplasma etching, such that a new technology for patterning copper had tobe developed, which is known as a copper damascene process. In thisprocess, the underlying silicon oxide insulating layer is patterned withopen trenches where the conductor should be filled in. A thick coatingof copper that significantly overfills the trenches is deposited on theinsulator and chemical mechanical planarization (CMP), also known aschemical mechanical polishing, is used to remove the copper to the toplevel of the trench.

Since copper may not be deposited efficiently by physical vapordeposition, for example, by sputter deposition, with a layer thicknesson the order of 1 μm and more, electroplating of copper and copperalloys is the currently preferred deposition method of formingmetallization layers. Although electroplating of copper is awell-established technique, reliably depositing copper over largediameter substrates, having a patterned surface including trenches andwires, is a challenging task for process engineers. At a first glance,it appears to be advantageous that the metal thickness profile acrossthe substrate surface may be formed as uniformly as possible. However,post-plating processes may require a differently shaped profile so as toassure proper device functionality of the completed integrated circuits.Currently, there is no effective copper dry etching method because ofproblems removing low volatility copper compounds. Presently, chemicalmechanical polishing (CMP) is used for removing excess copper. Since theCMP process is per se a highly complex process frequently exhibiting anintrinsic process non-uniformity, i.e., a non-uniform removal rateacross the substrate surface, it may be preferable to adapt the metalthickness profile to the post-plating process to achieve in total animproved process uniformity after the completion of the post-platingprocess. Therefore, electroplating tools are often configured so as toallow a variation of the metal profile, for instance by using multipleanodes on an ECD (electrochemical deposition) copper plating tool.

All current systems were using unpatterned test wafers to adjust theplating profile. FIG. 1 illustrates an adjustment scheme for adjusting aplating profile. In FIG. 1, an unpatterned test wafer 1 is coated in aplating tool 2 with copper. A four-point-probe 3 measures a copperprofile of the unpatterned coated wafer. A controller 4 compares themeasured data with a profile target and calculates corrections if themeasured copper profile does not match with the profile target. Thecontroller 4 then updates the tool settings of the plating tool 2. Theprofile target inputted to the controller 4 considers chemicalmechanical polishing characteristics of the chemical mechanicalpolishing (CMP) tool. The plating tool 2 is an electroplating systemhaving a plurality of individually drivable anode portions, therebydefining a multiple anode configuration. A substrate holder may beconfigured as a cathode and, by individually adjusting each anodecurrent, a plating profile across a substrate surface may be controlled.The tool settings are adjusted in repetitively running test wafers aslong as the difference between the profile target and the measuredprofile falls below a predetermined value.

Once appropriate tool settings have been found, a patterned productwafer may be plated with copper. This is exemplified in FIG. 2. Copperis electrochemically deposited with the plating tool 2 onto a patternedproduct wafer 5. The plating tool settings for base shaping of thedeposition profile for compensating chamber characteristics is done byqualification of unpatterned test wafers as described in connection withFIG. 1. Constant offsets are applied to these settings in order to takeinto consideration profile deviations due to the patterns on the productwafer. In case of a multi-anode plating tool, a constant offset isapplied to each of the anodes of the plating tool.

After plating the patterned product wafer, it is treated with chemicalmechanical polishing 6 in order to finish the copper wirings. By polishendpoint tracing 7, or other adequate measurements, for instance, motorcurrent control, post polish thickness or sheet resistance measurements,chemical mechanical polishing 6 parameters may be adjusted toappropriately remove excess copper. Since the plating tool settings arefixed once appropriate settings have been found, this method isdesignated as a static method.

It has to be noted that the characterization of the process illustratedin FIG. 2 needs to be done individually per layer and product if thereare significant differences in percentages of open areas, die sizes andwafer stepping. All these efforts lead to a consumption of a certainamount of wafers to find the right shaping, which adds cost and cycletime. The CMP process is very consumable-dependent. Therefore, aone-time snap shot is not always relevant for the whole population ofproduct wafers. Additionally, there is an individual operator and/orengineering dependence. A further drawback of the static method is thatprocess fluctuations cannot be compensated for. For instance, theelectrolyte concentration may change with time which leads to a changeof the plating profile. Anodes or cathodes may corrode with time suchthat the plating settings become inadequate. Chemical mechanicalpolishing conditions may change due to deterioration of the toolcharacteristics. As a consequence, additional qualification runs ofunpatterned test wafers have to be carried out in order to re-adjust thetool settings, i. e., the plating tool and the CMP tool.

FIG. 3 exemplifies some of these drawbacks. FIG. 3 a (left hand upperpart) shows an unpatterned test wafer 1 which has been coated withcopper in a chamber with tool A such that its deposition profile matcheswith the target profile. FIG. 3 b (right hand upper part) shows the samewith a different tool B. FIG. 3 c (left hand lower part) shows apatterned product wafer 5 which has been coated with copper in chambertool A using the same settings as in FIG. 3 a. As can be seen in FIG. 3c, the thickness profile is different as shown in FIG. 3 a due to achamber offset and the patterns on the product wafer 5. Chamber offsetmeans that the product wafer is not coated immediately after a testwafer run such that plating conditions like consumable status andchamber status due to aging may have changed. Also the patterns on theproduct wafer, like trenches and their width and depth, may influencethe electrical field that is necessary for the plating process. FIG. 3d(right hand lower part) shows another product wafer 5 which has beencoated in chamber tool B with copper. Even if the patterns on theproduct wafer are the same as in FIG. 3 c, and even if the profile of atest wafer is the same in chamber tool B and chamber tool A, the profileon the product wafer is different in FIGS. 3 d and 3 c due to plater andchamber offsets and wafer patterns.

In view of the global market forces to offer high quality products atlow prices, it is thus important to improve yield and process efficiencyto minimize production costs. In manufacturing modern integratedcircuits, 500 or more individual processes may be necessary to completethe integrated circuit, wherein failure in a single process step mayresult in a loss of the complete integrated circuit. It is thereforecrucial for manufacturing integrated circuits that each individual stepreliably has the desired result, thereby requiring as little as possibleresources.

The present disclosure is directed to various methods and systems thatmay avoid, or at least reduce, the effects of one or more of theproblems identified above.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order toprovide a basic understanding of some aspects of the invention. Thissummary is not an exhaustive overview of the invention. It is notintended to identify key or critical elements of the invention or todelineate the scope of the invention. Its sole purpose is to presentsome concepts in a simplified form as a prelude to the more detaileddescription that is discussed later.

Generally, the present disclosure is directed to a method of automaticdeposition profile targeting that leads to an automatic andself-sufficient process of plating targeting or other depositiontargeting of metal or dielectrics on given deposition and chemicalmechanical polishing (CMP) equipment.

In particular, there is provided a method of automatic depositionprofile targeting for depositing a material with a position-dependentcontrollable deposition tool, for instance, a multi-anode plating tool,but not limited thereto, such that the deposition profile matches withpolishing characteristics of the CMP tool in order to achieveappropriate copper wiring structures in semiconductor chip technology.The method comprises the steps of depositing material, e.g., copper, ona patterned product wafer, measuring an actual thickness profile ofdeposited material and generating respective measurement data, feedingthe measurement data to an advanced process control model andcalculating individual corrections for deposition parameters in theposition-dependent controllable deposition tool. There is thus providedan objective and fast method for an automatic and product measurementbased deposition shaping, which does not require manual shapingexperiments. The method provides both dynamically targeting depositionprofile during running of a production process and automatically findingplating process recipes for a new layer/product combination which matchthe profile targets.

As soon as a process recipe for the product/layer combination has beenfound, the advanced process control (APC) is able to collect processrelevant data and provides dynamically adjusted product/layer correctionfactor optimizing for plating tool settings. The advanced processcontrol may further provide improved initial settings for newproducts/layer combinations such that time for adjusting a new processfor a new product/layer combination may be saved. In addition, theadvanced process control provides a user-friendly set of parameters fordocumentation and charting of relevant parameters to avoid anuncontrolled APC black box behavior.

According to one illustrative embodiment, the advanced process controlincludes models which can predict plating behavior. For instance, theremay be included a model describing a dependency between a depositionprofile target and a chemical mechanical polishing (CMP) toolcharacteristic and a CMP tool history, a model of a dependency between adeposition profile and underlying product wafer structures, a model of adependency between a deposition profile and plating tool characteristicsand chamber characteristics, a model of a dependency between adeposition profile and a plating tool history and a chamber history, anda model describing a relation between an unpatterned test wafer and apatterned product wafer. Thus, accurate initial settings for a newproduct layer combination may be calculated and process fluctuations maybe compensated for more quickly and accurately.

According to another illustrative embodiment, the corrections arecalculated based on a difference between an actual deposition profileand a target deposition profile. Furthermore, the APC model isrepeatedly recalculated and updated based on the calculated correctionsuntil the difference between the actual deposition profile and thetarget deposition profile is smaller than a predetermined value.Subsequently, a new set of model data is implemented in the APCincluding relevant process parameters selected at least from the groupcomprising pattern density, etch depth, trench width, wafer stepping,material and crystal orientation of underlayer, consumable status,hardware settings, and chamber geometry. This leads to a self consistentmethod of profile targeting which does not require test measurements.

According to a further illustrative embodiment, a virtual test wafertarget and a virtual test wafer profile is calculated from the measuredproduct wafer, and process parameter corrections may be calculated basedon a difference between the virtual test wafer profile and the virtualtest wafer product. A particular advantage is that calculating virtualtest wafer profiles and virtual test wafer targets reduces the data to auser friendly and intuitive format. A further advantage is that the usedmodels may be validated and adjusted by processing a test wafer.

In yet another illustrative embodiment, there is provided a system forautomatic deposition profile targeting according to the above-describedmethods comprising a position-dependent controllable plating tool forelectrochemical depositing copper, a measurement tool to determine adeposition profile of deposited copper, a chemical mechanical polishingtool (CMP) and an advanced process controller connected with themeasurement tool and the position-dependent controllable plating tool,wherein at least one of the following models is implemented in theadvanced process controller: a model of a dependency between adeposition profile target and CMP tool characteristics and CMP toolhistory; a model of a dependency between a deposition profile andunderlying product wafer structures; a model of a dependency between adeposition profile and plating tool characteristics and chambercharacteristics; a model of a dependency between a deposition profileand a plating tool history and chamber history; and a model describing arelation between an unpatterned test-wafer and a patterned productwafer, wherein the advanced process controller is configured tocalculate a virtual test wafer profile and a virtual test wafer targetfrom measured profile of a product wafer, wherein the advanced processcontroller is configured to calculate process parameter correctionsbased on a difference between the calculated virtual test wafer profileand the calculated virtual test wafer target, for updating a processrecipe of the plating tool, wherein the corrections are calculated basedon a difference between an actual deposition profile and a targetdeposition profile, wherein the APC model is repeatedly recalculated andupdated based on the corrections until the difference between the actualdeposition profile and the target deposition profile is smaller than apredetermined value, and wherein a new set of model data is implementedin the APC, including relevant process parameters selected from at leastany one of the group comprising pattern density, etch depth, trenchwidth, wafer stepping, material and crystal orientation of underlayer,consumable status, hardware settings, and chamber geometry.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be understood by reference to the followingdescription taken in conjunction with the accompanying drawings, inwhich like reference numerals identify like elements, and in which:

FIG. 1 illustrates a method for adjusting tool settings of a platingtool by use of an unpatterned test wafer according to the state of theart;

FIG. 2 illustrates the processing of a patterned product wafer with aplating tool adjusted with the settings determined in the methodaccording to FIG. 1;

FIG. 3 illustrates drawbacks of a static targeting method according toFIGS. 1 and 2;

FIG. 4 illustrates schematically the method of automatic depositionprofile targeting according to the present disclosure; and

FIG. 5 illustrates the advantages of the method schematicallyillustrated in FIG. 4.

While the subject matter disclosed herein is susceptible to variousmodifications and alternative forms, specific embodiments thereof havebeen shown by way of example in the drawings and are herein described indetail. It should be understood, however, that the description herein ofspecific embodiments is not intended to limit the invention to theparticular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

Various illustrative embodiments of the invention are described below.In the interest of clarity, not all features of an actual implementationare described in this specification. It will of course be appreciatedthat in the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

The present subject matter will now be described with reference to theattached figures. Various structures, systems and devices areschematically depicted in the drawings for purposes of explanation onlyand so as to not obscure the present disclosure with details that arewell known to those skilled in the art. Nevertheless, the attacheddrawings are included to describe and explain illustrative examples ofthe present disclosure. The words and phrases used herein should beunderstood and interpreted to have a meaning consistent with theunderstanding of those words and phrases by those skilled in therelevant art. No special definition of a term or phrase, i.e., adefinition that is different from the ordinary and customary meaning asunderstood by those skilled in the art, is intended to be implied byconsistent usage of the term or phrase herein. To the extent that a termor phrase is intended to have a special meaning, i.e., a meaning otherthan that understood by skilled artisans, such a special definition willbe expressly set forth in the specification in a definitional mannerthat directly and unequivocally provides the special definition for theterm or phrase.

It is to be noted that the detailed description will refer toelectroplating of a metal such as copper, on substrates such as thosetypically used in semiconductor fabrication, since the presentdisclosure is particularly useful in a process sequence with sensitivepost-plating processes, such as chemical mechanical polishing (CMP). Itwill be readily appreciated, however, that the present disclosure isapplicable to any plating process with an externally impressed current(electroplating), of any types of substrates requiring a specifieddeposition profile on a substrate surface or a portion thereof.Moreover, although the description refers to a plating tool, this methodcan also be applied to any deposition tool which can control depositionprofile and which requires post-deposition processes such as etching andpolishing. Thus, the present disclosure is to be understood as not beingrestricted to a specific type of deposition tool unless depositions areexplicitly set forth in the claims.

One particular feature of this disclosure is that an actual thicknessprofile of deposited material on a product wafer is measured andcorrections for the deposition tool is calculated on the basis of anadvanced process control (APC) model in order to compensate productionline fluctuations or in order to find a parameter set for the depositiontool such that the deposition profile target is met. Thus, no testwafers are required to adjust the tool settings for a particular layeror product. The method adjusts the tool settings in a self-consistentprocess until the intended profile target is achieved. Further, bytracking and storing production parameters, the advanced productioncontrol model may be continuously improved and updated such that thesettings for a particular deposition target may be found quickly andmore accurately. Moreover, the collected data may be presented in a moreuser friendly way of virtual test wafer targets and virtual test waferprofiles which may be used in turn to validate the APC models.

FIG. 4 illustrates the method of this disclosure. A patterned productwafer 50 is coated with copper in a plating tool 20. Subsequently, thedeposition profile of the deposited copper is measured in a profilemeasurement tool 70. If the actual measured copper profile matches withthe target profile, the product wafer may be forwarded to the chemicalmechanical polishing tool 60 for further processing. The measurementdata of the profile measurement tool are fed to the advanced processcontrol 80 which may readjust the tool settings of the plating tool 20if necessary. The APC 80 may optionally collect the tool parameters fromthe plating tool 20 and the CMP tool 60. Further, the APC 80 may storethe measured and the calculated parameters in a data base.

The plating tool 20 may be a typical conventional electroplating systemincluding a reactor vessel with a plurality of individually drivableanode portions thereby defining a multiple anode configuration. Theplating tool 20 may be a so-called fountain type reactor, in which anelectrolyte solution is directed from the bottom of the reactor vesselto the top side and is then re-circulated by a pipe connecting an outletwith a storage tank, which in turn is connected to an inlet provided asa passage through the anode. The electroplating system may furthercomprise a substrate holder that is configured to support a substrate,such as the patterned product wafer 50, so as to expose a surface ofinterest to the electrolyte. Moreover, the substrate holder may beconfigured to connect as a cathode. In a typical configuration, a thincurrent distribution layer, typically provided by sputter deposition, isformed on the surface of the substrate 50 that will receive the metallayer. After mounting the substrate on the substrate holder andconnecting the current distribution layer with a power source via thesubstrate holder, an electrolyte flow is created within the reactorvessel by activating a pump. By applying appropriate voltages betweenthe multiple anode configuration and the cathode, copper is deposited onthe product wafer 50 depending on respective currents between thecathode and each of the plurality of anode portions. The deposition ofmetal on the substrate 50 is determined by the flow of electrolyte andthe arrangement of the multiple anode configuration, since the localdeposition rate of metal on a specific area of a surface of thesubstrate depends on the number of ions arriving at this area. Theresulting thickness profile is determined not only by the individualcurrents flowing through any one of the plurality of anodes, but is alsodetermined by the characteristics of the reactor vessel, the electrolytesolution, and the characteristics of the wafer itself. Generally, theplating profile may be described by the following formula 1:

M(r)=S(r)·I(r)·t   (1)

M(r) is the thickness profile of the deposited copper. Please note thatin this case a circular symmetry is assumed wherein the thickness of thecopper depends only on the radius r in a polar co-ordinate system. As aperson skilled in the art would appreciate, limiting the dependency onlyon the radial coordinate serves only for illustrative purposes. As theperson skilled in the art knows, an angular dependence of the thicknessprofile in case of a polar coordinate system is also possible. I(r)designates the local current at the coordinate r. t is the time ofcurrent flow. I(r)·t designates the total deposited charge Q at theradius r. Although it is assumed in a first approach that all of thetotal charge Q is deposited at the respective radius r, the realsituations showed that there are many influences which disturb thedeposition of the copper having the charge Q at the particular radialposition r. This influence is taken into consideration with a correctionfactor, a so-called sensitivity function S(r) which subsumes theaforementioned reactor vessel and substrate characteristics.

The control over the deposition profile M(r) is achieved by theparticular multi-anode configuration which allows local adjustment ofthe deposition current due to the configuration of the anodes. If, forinstance, the anodes are arranged in a circular shape at differentradii, the deposition profile M(r) may be influenced radius-dependent.

The total amount of deposited charges/copper is given according toformula 2:

$\begin{matrix}{Q = {{\int_{r = {- R}}^{+ R}{{I(r)} \cdot t \cdot {r}}} = {I_{total} \cdot t}}} & (2)\end{matrix}$

Since, in a multi-anode configuration, the total current I_(total) isrealized by the sum of the individual currents of the respective anodes,the total current I_(total) may be described as in the following formula3:

I _(total) =I _(Anode1) +I _(Anode2) +I _(Anode3)+  (3)

Formula 2 may then be written in a discreet form according to formula 4:

$\begin{matrix}\begin{matrix}{Q = {\sum\limits_{i}{{I_{Anodei}\left( r_{i} \right)} \cdot t}}} \\{= {\left( {{I_{{Anode}\; 1}\left( r_{1} \right)} + {I_{{Andoe}\; 2}\left( r_{2} \right)} + {I_{{Anode}\; 3}\left( r_{3} \right)} + \ldots}\; \right) \cdot t}}\end{matrix} & (4)\end{matrix}$

Since the deposited charge/copper is not completely under the control ofa respective anode and its position, which is subsumed with thesensitivity function S(r), the currents of respective anodes have to becorrected. Formula 5 gives a more general expression for externalinfluences:

S(r)=S(r, A ₁(r), A ₂(r), . . . )   (5)

S(r) represents the aforementioned sensitivity function for particularpositions r, indicating the affinity of particular positions r fordepositing a charged particle such as copper. A₁(r) and A₂(r) mayrepresent, for instance, electrolyte concentration at a particularposition r depending on, for instance, consumable status and flowprofile of the electrolyte. Also, pattern density, etch depth, trenchwidth, wafer stepping, material and crystal orientation of an underlayeron the substrate may have an influence on the sensitivity parameterS(r). The sensitivity factor requires a correction of each of thecurrents corresponding to particular anodes. This may be, for instance,considered by applying a particular correction factor to each anodecurrent as exemplified, for instance, with formula 6:

I_(total) =I _(Anode1) ·cf1+I _(Anode2) cf2+I _(Anode3) ·cf3+  (6)

Formula 6 indicates that a correction factor cf1, cf2, cf3 . . . isapplied to the respective anode current I_(Anode1), I_(Anode2),I_(Anode3) . . . in order to achieve the intended deposition profile.

It has to be understood that the corrections of the anode current is notrestricted to a correction factor, but an offset may also be appliedindividually to each anode current. Further, the described plating toolis not limited to a fountain-type plating tool. Other types of platingtools such as electrolyte baths and the like may be used as well. Thus,the present disclosure is to be understood as not being restricted to aspecific type of electroplating tool.

The subsequent measurement with the profile measurement tool 70 iscarried out by any suitable measurement tools, e.g., Rudolf MetaPulse,Jordan Valley or AMS. The respective measurement data are fed to the APC80, which have implemented models generally describing the sensitivityfactor S(r) (see formula 5).

FIG. 5 illustrates some of the advantages of the present disclosure.Similar to FIG. 3, FIG. 5 a shows an unpatterned test wafer which hasbeen coated with copper in a chamber with tool A such that itsdeposition profile matches with the target profile. FIG. 5 b shows thesame with a different tool B. FIG. 5 d shows a patterned product waferwhich has been coated with copper in chamber tool A using the samesettings as in FIG. 5 a. As can be seen in FIG. 5 d, the thicknessprofile is different than that as shown in FIG. 5 a due to a chamberoffset and the patterns on the product wafer. FIG. 5 e shows anotherproduct wafer patterns different than that in FIG. 5 d and which hasbeen coated in chamber tool B with copper. All data are collected andprocessed in the APC. This is illustrated with FIG. 5 c and 5 f. FIG. 5c and 5 f symbolizes how the APC calculates process models based onmeasurement data. Thus, the APC may provide appropriate corrections foradjusting anode currents.

According to the disclosure, the APC may be used in two different modes.

First Operating Mode:

In the first operating mode, the APC is continuously active and uses themeasurement data from the profile measurement tool 70 to adjust theplating tool settings continuously during successively processedsubstrates. An example of the method is given as follows.

A substrate coated with copper by the plating tool 20 is measured withthe profile measurement tool 70. If the APC 80 detects that the actualcopper profile is different from the profile target, the APC calculatesa correction of the tool settings, i.e., corrections for each of theanode currents I_(Anode1), I_(Anode2), I_(Anode3) on the basis offormula 1. For this purpose, a discrete version of formula 1 has to beimplemented in the APC 80.

More concretely, formula 1 has been implemented in a discrete form asexemplified in formula 7:

$\begin{matrix}{\begin{pmatrix}M_{r\; 1} \\M_{r\; 2} \\M_{r\; 3}\end{pmatrix} = {\begin{pmatrix}S_{{r\; 1},1} & S_{{r\; 1},2} & S_{{r\; 1},3} \\S_{{r\; 2},1} & S_{{r\; 2},2} & S_{{r\; 2},3} \\S_{{r\; 3},1} & S_{{r\; 3},2} & S_{{r\; 3},3}\end{pmatrix} \cdot \begin{pmatrix}I_{r\; 1} \\I_{r\; 2} \\I_{r\; 3}\end{pmatrix} \cdot t}} & (7)\end{matrix}$

In formula 7, it is assumed that the plating tool has three anodes at athe radial position r1, r2 and r3. The respective anode currents aredesignated as I_(r1), I_(r2) and I_(r3). The thickness of the depositedcopper at a respective location r1 is designated as M_(r1). Thethickness of the copper at the anode locations r2 and r3 are designatedaccordingly as M_(r2) and M_(r3). It has to be noted that, in thisillustrative example, only three thickness positions are considered,namely at r1, r2 and r3. The person skilled in the art knows, however,that the number of thickness positions and the number of anodes need notbe the same. For instance, the model may be extended to consider fourelectrodes and, for instance, ten thickness profile locations M. In thiscase, vector M (see formula 8) has ten elements and vector I (seeformula 8) has four elements.

M=S·I·t   (8)

Formula 8 shows the matrix notation of formula 7 in a short vectornotation. The parameter t indicates the time during which the current Iflows.

The matrix S takes into consideration corrections due to chamber andtool characteristics and substrate characteristics as already outlinedabove. For instance, if there would be no influence from the chamber,the electrolyte concentration, the flow conditions or the patterndensity on the substrate, the matrix S would be the unity matrix. Thatmeans that current I_(r1) deposits copper only at the position r1 havingthe thickness M_(r1). In this case, in formula 7, the values S_(r1,1),S_(r2,2), and S_(r3,3) have the value 1 and the remainder elements are0. On the other hand, if, for instance, the electrolyte flow transportscharges from anode 1 (current I_(r1)) to the locations r1, r2 and r3,the matrix S is no longer a diagonal matrix. If we assume, for instance,that 50% of I_(r1) deposits at M_(r1), 25% of I_(r1) deposits at M_(r2)and 25% of I_(r1) deposits at M_(r3), the component S_(r1,1) may be setto the value of 0.5, the matrix component S_(r2,1) may be set to 0.25and the matrix component S_(r3,1) may be set to the value 0.25. It hasto be noted that, in the above example, the values of the matrix Scomponents are only relative values exemplifying the principle and donot consider absolute deposition values.

If the APC 80 recognizes a difference AM between the actual measuredprofile and the target profile, the APC may calculate corrections of theanode currents according to formula 9:

$\begin{matrix}{{\begin{pmatrix}{\Delta \; I_{r\; 1}} \\{\Delta \; I_{r\; 2}} \\{\Delta \; I_{r\; 3}}\end{pmatrix} \cdot t^{- 1}} = {\begin{pmatrix}S_{{r\; 1},1} & S_{{r\; 1},2} & S_{{r\; 1},3} \\S_{{r\; 2},1} & S_{{r\; 2},2} & S_{{r\; 2},3} \\S_{{r\; 3},1} & S_{{r\; 3},2} & S_{{r\; 3},3}\end{pmatrix}^{- 1} \cdot \begin{pmatrix}{\Delta \; M_{r\; 1}} \\{\Delta \; M_{r\; 2}} \\{\Delta \; M_{r\; 3}}\end{pmatrix}}} & (9)\end{matrix}$

In formula 9, ΔI_(r1), ΔI_(r2) and ΔI_(r3) are the correction valueswhich have to be applied as an offset to the anode currents. The valuesΔM_(r1), ΔM_(r2) and ΔM_(r3) are the measured differences between theactual thickness and the targeted thickness at the positions r1, r2 andr3. Matrix S⁻¹ in formula 9 is the inverse matrix of S in formulae 7 and8. Formula 10 again shows the short vector notation of formula 9.

ΔI·t ⁻¹ =S ⁻¹ ·ΔM   (10)

In the continuous operation mode (first operating mode), the values formatrix S are given. With the given matrix S, even small processfluctuations may be compensated for in successively processedsubstrates.

The determination of the matrix values S and start values for anodecurrents is carried out in the profile targeting mode (second operatingmode), which is explained in more detail below.

Second Operating Mode:

In the profile targeting mode, two situations have to be distinguished.In the first situation, there already exists a database for a pluralityof process situations. The database may be incorporated in the form ofan expert system containing a set of stored data, for instance,measurement data, such as pattern density for a plurality of productsand layers, chamber characteristics, tool settings and profilemeasurement data, or this database may already be implemented in theadvanced process control model in the form of, for instance, asensitivity matrix S (see formulae 5, 7, 8, 9 and 10). Therepresentation of a plurality of data sets in the form of a singlematrix may be considered as a data reduction which has the advantagethat no additional storage capacity has to be provided. It has to benoted that the database may comprise a plurality of sensitivitymatrices, each of them corresponding to a particular product/layercombination including relevant process and equipment parameters.

In a particular case where a new layer of a new product has to beproduced, certain initial values have to be inputted in order todetermine appropriate start values for the plating process. Such valuesmay be characteristics of the substrate, such as pattern density, etchdepth, trench width, wafer stepping, material and crystal orientation ofunderlying materials and the like. Further parameters could be chambercharacteristics such as flow geometry for the electrolyte, consumablestatus-like concentration of electrolyte, electrode condition such aselectrode history and condition concerning corrosion and the like.Further, a target profile has to be inputted into the APC. The APC maylook for appropriate data sets in the database which match with theinputted values as far as possible and calculates with the foundsensitivity matrix initial settings for the anode currents by use of amathematical model according to formula 11, which corresponds to aninverse of formula 7.

$\begin{matrix}{{\begin{pmatrix}I_{r\; 1} \\I_{r\; 2} \\I_{r\; 3}\end{pmatrix} \cdot t^{- 1}} = {\begin{pmatrix}S_{{r\; 1},1} & S_{{r\; 1},2} & S_{{r\; 1},3} \\S_{{r\; 2},1} & S_{{r\; 2},2} & S_{{r\; 2},3} \\S_{{r\; 3},1} & S_{{r\; 3},2} & S_{{r\; 3},3}\end{pmatrix}^{- 1} \cdot \begin{pmatrix}M_{r\; 1} \\M_{r\; 2} \\M_{r\; 3}\end{pmatrix}_{target}}} & (11)\end{matrix}$

In formula 11, I_(r1), I_(r2) and I_(r3) designate respective initialvalues for anode currents. M_(r1), M_(r2) and M_(r3) designate thetarget thicknesses of the copper at the anode locations r2, r2 and r3.

The better the model is, the better are the initial values for the anodecurrents and the better is the result of the plating profile. That meansthat, without the usage of test wafers, it is possible to very quicklyachieve a process recipe for achieving the intended results.

If there does not exist any data, the APC assumes initial values for thesensitivity matrix S. For instance, it may use the identity matrix asthe sensitivity matrix. The first process run leads to particulardeviations between the measured actual deposition profile and thedeposition profile target. The APC now calculates a new sensitivitymatrix based on the actual measured profile and the corresponding anodecurrents, for instance, by use of formula 12.

$\begin{matrix}\begin{matrix}{{\begin{pmatrix}I_{r\; 1} \\I_{r\; 2} \\I_{r\; 3}\end{pmatrix} \cdot \begin{pmatrix}M_{r\; 1}^{- 1} & M_{r\; 2}^{- 1} & M_{r\; 3}^{- 1}\end{pmatrix}} = \begin{pmatrix}{I_{r\; 1} \cdot M_{r\; 1}^{- 1}} & {I_{r\; 1} \cdot M_{r\; 2}^{- 1}} & {I_{r\; 1} \cdot M_{r\; 3}^{- 1}} \\{I_{r\; 2} \cdot M_{r\; 1}^{- 1}} & {I_{r\; 2} \cdot M_{r\; 2}^{- 1}} & {I_{r\; 2} \cdot M_{r\; 3}^{- 1}} \\{I_{r\; 3} \cdot M_{r\; 1}^{- 1}} & {I_{r\; 3} \cdot M_{r\; 2}^{- 1}} & {I_{r\; 3} \cdot M_{r\; 3}^{- 1}}\end{pmatrix}} \\{= \begin{pmatrix}S_{{r\; 1},1} & S_{{r\; 1},2} & S_{{r\; 1},3} \\S_{{r\; 2},1} & S_{{r\; 2},2} & S_{{r\; 2},3} \\S_{{r\; 3},1} & S_{{r\; 3},2} & S_{{r\; 3},3}\end{pmatrix}_{new}^{- 1}}\end{matrix} & (12)\end{matrix}$

In formula 12, I_(r1), I_(r2) and I_(r3) designate actual values foranode currents. M_(r1), M_(r2) and M_(r3) designate the measuredthicknesses of the copper at the anode locations r2, r2 and r3.

After the new inverse sensitivity matrix S⁻¹ has been calculated, a newset of anode current settings are calculated according to formula 13 anda new process run is carried out.

$\begin{matrix}{{\begin{pmatrix}I_{r\; 1} \\I_{r\; 2} \\I_{r\; 3}\end{pmatrix} \cdot t^{- 1}} = {\begin{pmatrix}S_{{r\; 1},1} & S_{{r\; 1},2} & S_{{r\; 1},3} \\S_{{r\; 2},1} & S_{{r\; 2},2} & S_{{r\; 2},3} \\S_{{r\; 3},1} & S_{{r\; 3},2} & S_{{r\; 3},3}\end{pmatrix}_{new}^{- 1} \cdot \begin{pmatrix}M_{r\; 1} \\M_{r\; 2} \\M_{r\; 3}\end{pmatrix}_{target}}} & (13)\end{matrix}$

This method is carried out repeatedly until the difference between thetarget profile and the current measured profile does not exceed acertain value.

As soon as an appropriate matrix S for the sensitivity matrix has beenfound, it is implemented in the APC model together with theabovementioned parameters (pattern density, chamber characteristics,etc.). After several process recipes have been found for different layerproduct combinations that also include particular sensitivity matrixes,the APC will be in a state where initial settings for anode currents maybe found very quickly by, for instance, interpolating initial parametersand corresponding initial sensitivity matrixes.

For instance, if there exists a process recipe for a wafer having apattern density D1 and a pattern density D2 in the database as well ascorresponding sensitivity matrices, a possible starting point for a newprocess of a new product/layer combination may be to form a mean valuebetween the matrix components relating to pattern density D1 and D2.Based on this new mean sensitivity matrix, respective initial settingsfor the anode currents may be calculated.

Thus, the described method leads to an automatic and self-sufficientprocess of plating targeting on given deposition and CMP equipmentwherein manual shaping experiments may be avoided and which providesimproved start settings of the plating tool. Further, this method allowsa dynamic adjustment of process fluctuations and optimizes respectivecorrections.

The above model also allows calculating a virtual test wafer target anda virtual test wafer profile. To achieve this, formula 7 may be used tocalculate virtual wafer profiles and virtual wafer targets by using anappropriate sensitivity matrix. A respective matrix could be obtained,for instance, by test wafer measurements which have to be carried outonly one time to characterize equipment properties. Another possibilitywould be to interpolate data from the database to eliminate waferinfluences from the sensitivity matrix. Thus, a theoretical profile on atest wafer may be calculated. By running test wafers, the APC model maybe validated or, if necessary, corrected and updated. Moreover,calculating virtual test wafer data provides a user friendly set of datain order to judge the performance of the APC model.

It has to be understood that the above presented APC represents only anillustrative example and the disclosure should be not limited thereto.The person skilled in the art knows that other equivalentrepresentations of the models are possible. For instance, collectingparameters and measurement data in an expert system which allowsinterpolation between data points and which has implemented decisionrules is also possible. Alternatively, representing the data aspolynomial or spline interpolated functions may be considered.

As a result, the present disclosure provides a technique which enablesan automatic deposition profile targeting for electrochemicallydepositing copper with a multi-anode plating tool which isself-consistent and which does not require time-consuming test waferruns. Further, this method allows dynamic compensation of processfluctuations and is able to reduce data efficiently and in a userfriendly way.

The particular embodiments disclosed above are illustrative only, as theinvention may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. For example, the process steps set forth above may beperformed in a different order. Furthermore, no limitations are intendedto the details of construction or design herein shown, other than asdescribed in the claims below. It is therefore evident that theparticular embodiments disclosed above may be altered or modified andall such variations are considered within the scope and spirit of theinvention. Accordingly, the protection sought herein is as set forth inthe claims below.

1. A method of automatic deposition profile targeting forelectrochemically depositing copper with a position-dependentcontrollable plating tool, comprising the steps of: depositing copper ona patterned product wafer; measuring an actual thickness profile of thedeposited copper and generating respective measurement data; feeding themeasurement data to an advanced process control (APC) model; andcalculating individual corrections for plating parameters in theposition-dependent controllable plating tool.
 2. The method of claim 1,wherein the advanced process control (APC) model includes at least oneof a model of a dependency between a deposition profile target andchemical/mechanical polishing (CMP) tool characteristics and CMP toolhistory, a model of a dependency between a deposition profile andunderlying product wafer structures, a model of a dependency between adeposition profile and plating tool characteristics and chambercharacteristics, and a model of a dependency between a depositionprofile and a plating tool history and chamber history, wherein theadvanced process control (APC) model predicts plating behavior based onthese models.
 3. The method of claim 2, wherein the model of thedependency between a deposition profile and underlying product waferstructures includes at least one of the following product parameters:pattern density, etch depth, trench width, wafer stepping and materialand crystal orientation of underlayer.
 4. The method of claim 2, whereinthe model of the dependency between a deposition profile and platingtool and chamber characteristics includes at least one of the followingtool parameters: consumable status, hardware settings and chambergeometry.
 5. The method of claim 2, further comprising calculating avirtual test wafer target and a virtual test wafer profile by use of amodel implemented in the APC describing a relation between anunpatterned test wafer and a patterned product wafer.
 6. The method ofclaim 5, wherein the actual deposition profile is the calculated virtualtest wafer profile and the target profile is the calculated virtual testwafer target.
 7. The method of claim 2, wherein the corrections arecalculated based on a difference between an actual deposition profileand a target deposition profile, and wherein the corrections comprise atleast one of position-dependent offsets and position-independentoffsets.
 8. The method of claim 7, wherein the actual deposition profileis the calculated virtual test wafer profile and the target profile isthe calculated virtual test wafer target.
 9. The method of claim 7,further comprising: repeatedly re-calculating and updating said APCmodel based on said corrections until the difference between the actualdeposition profile and the target deposition profile is smaller than apredetermined value; and implementing a new set of model data includingrelevant process parameters as set forth in any one of the claims 3 and4.
 10. The method of claim 7, wherein the actual deposition profile ismeasured on the actually processed product wafer and the depositiontarget profile is the target profile for the patterned product wafer.11. The method of claim 7, wherein the corrections are at least one ofindividual offsets and correction factors for each anode current of amulti-anode plating tool in a multi-anode electrochemical depositionapparatus.
 12. The method of claim 2, wherein the APC is in acontinuously active mode to compensate for fluctuations within aproduction lot, and wherein corrections are applied to a subsequentlyprocessed wafer.
 13. The method of claim 2, wherein the APC is in atargeting mode to achieve a target profile in successively processedproduction lots, and wherein corrections are applied to a subsequentlyprocessed lot.
 14. The method of claim 5, further comprising collectingdata of calculated virtual test wafer targets and virtual test waferprofiles.
 15. The method of claim 14, further comprising processing atest wafer, measuring deposition profile, comparing the measured profilewith the virtual test wafer profiles and calculating testwafer-to-product response functions in order to adjust the modeldescribing the relation between an unpatterned test wafer and thepatterned product wafer.
 16. The method of claim 15, further comprisingvalidating the APC model by running a test wafer and comparing measuredtest wafer profiles with the calculated virtual test wafer profiles. 17.The method of claim 15, further comprising calculating from thecollected data at least one of a layer-to-layer response function or aproduct-to-product response function.
 18. A method of automaticdeposition profile targeting for depositing a material with aposition-dependent controllable plating tool, comprising the steps of:depositing a material on a patterned product wafer; measuring an actualthickness profile of the deposited metal and generating respectivemeasurement data; feeding the measurement data to an advanced processcontrol (APC) model that includes at least one of a model of adependency between a deposition profile target and CMP toolcharacteristics and CMP tool history, a model of a dependency between adeposition profile and underlying product wafer structures, a model of adependency between a deposition profile and plating tool characteristicsand chamber characteristics, a model of a dependency between adeposition profile and a plating tool history and chamber history, and amodel describing a relation between an unpatterned test wafer and apatterned product wafer, wherein the advanced process control (APC)model predicts plating behavior based on these models; and calculatingindividual corrections for plating parameters in the position-dependentcontrollable plating tool.
 19. The method of claim 18, wherein thecorrections are calculated based on a difference between an actualdeposition profile and a target deposition profile, and wherein thecorrections comprise at least one of position-dependent offsets andposition-independent offsets, and wherein the method further comprises:repeatedly re-calculating and updating said APC model based on saidcorrections until the difference between the actual deposition profileand the target deposition profile is smaller than a predetermined value;and implementing a new set of model data including relevant processparameters selected at least from the group comprising pattern density,etch depth, trench width, wafer stepping, material and crystalorientation of underlayer, consumable status, hardware settings andchamber geometry.
 20. The method of claim 18, further comprisingcalculating a virtual test wafer target and a virtual test wafer profileby use of the model describing a relation between an unpatterned testwafer and a patterned product wafer.
 21. The method of claim 20, furthercomprising processing a test wafer, measuring a deposition profile,comparing the measured profile with the virtual test wafer profile andcalculating test wafer-to-product response functions to update the modeldescribing the relation between the unpatterned test wafer and thepatterned product wafer.
 22. The method of claim 18, further comprisingcalculating process parameter corrections based on a difference betweenthe virtual test wafer profile and the virtual test wafer target,wherein the corrections comprise at least one of position-dependentoffsets and position-independent offsets.
 23. A system for automaticdeposition profile targeting, comprising: a position-dependentcontrollable plating tool for electrochemically depositing copper; ameasurement tool to determine a deposition profile of deposited copper;a chemical mechanical polishing tool (CMP); and an advanced processcontroller connected with the measurement tool and theposition-dependent controllable plating tool; wherein at least one ofthe following models is implemented in the advanced process controller:a model of a dependency between a deposition profile target and CMP toolcharacteristics and CMP tool history, a model of a dependency between adeposition profile and underlying product wafer structures, a model of adependency between a deposition profile and plating tool characteristicsand chamber characteristics, a model of a dependency between adeposition profile and a plating tool history and chamber history, and amodel describing a relation between an unpatterned test wafer and apatterned product wafer; wherein the advanced process controller isconfigured to calculate a virtual test wafer profile and a virtual testwafer target from measured profile of a product wafer; wherein theadvanced process controller is configured to calculate process parametercorrections based on a difference between the calculated virtual testwafer profile and the calculated virtual test wafer target, for updatinga process recipe of the plating tool; wherein the corrections arecalculated based on a difference between an actual deposition profileand a target deposition profile, and wherein the corrections comprise atleast one of position-dependent offsets and position-independentoffsets; wherein said APC model is repeatedly re-calculated and updatedbased on said corrections until the difference between the actualdeposition profile and the target deposition profile is smaller than apredetermined value; and wherein a new set of model data is implementedin the APC including relevant process parameters selected from at leastany one of the group comprising pattern density, etch depth, trenchwidth, wafer stepping, material and crystal orientation of underlayer,consumable status, hardware settings and chamber geometry.